Motor.



No. 721,229. PATEN'I'ED FEB. 24, 1903.

0. H. & A. P. PIEPER. MOTOR.

APPLICATION FILED SEPT. 20, 1901.

110 KDDEL.

umunn Wiznesses- Inventors,

Attorney UNITED STATES PATENT OFFICE.

OSCAR H. PIEPER AND ALPI-IONSE F. PIEPER, OF ROCHESTER, NEW YORK.

MOTOR.

SPECIFICATION formingpart of Letters Patent N 0. 721,229, dated February24, 1903.

Application filed September 20, 1901. Serial No. 75,923. (No model.)

To all whom it may concern: I

Be it known that we, OSCAR H. PIEPER and ALPHONSE F. PIEPER, ofRochester, in the county of Monroe and State of New York,have inventedcertain new and useful Improvements in Motors; and we do hereby declarethe following to be a full, clear, and exact description of the same,reference being had to the accompanying drawings, forminga part of thisspecification, and to the reference characters marked thereon.

Our present invention relates to electric motors adapted for alternatingcurrents and to certain improvements relating to and means forcontrolling them, whereby they may be started with the necessary torque,and when the armature is under full speed it can be instantly stoppedand, if desired, its direction of movement reversed without the use ofclutches, brakes, or other mechanical holding devices.

The invention, which is designed more particularly for small motorsintended for operating dental engines or machines where accurate speedregulation is the leadingrequisite, relates to alternating-currentmotors of the direct-current type having the usual laminatedfield-magnets and the windings designed for a relatively highelectromotive force or relatively high self-induction, armature-coilsdesigned for a relatively low electromotive force or having a relativelylow self-induction, commutator and commutatorbrushes arranged at theneutral point, said field and armature windings being connected inseries; and the novel features of the invention relate to the control ofthe speed of such motors by the employment of an inductionwinding inshunt with the armature-brushes, and the accurate regulation of themotor is accomplished by varying the turns on the inductive winding.

The drawing shows a diagrammatic view illustrating our motor and themeans for regulating the same In the motor shown in the drawing, 1indicates a laminated field-magnet of the ring type, having thepole-pieces 2 and the fieldwindings 3, designed for a relatively highelectromotive force or relatively high self-induction.

t indicates the armature, provided with the armature-coils 5, designedfor a relatively low electromotive force or having a relatively lowself-induction, said coils being connected at intervals with sections 6of the commutator.

8 and 18 indicate the commutator-brushes, cooperating with thecommutator and ar-' ranged to contact with the coils which are in theneutral point of the magnet, being at an angle of ninety degrees to theaxis of the poles.

In the drawing the source of current for supplying the motor is atransformer, (indicated by T,) the primary coil 9 being in thehigh-tension circuit and the secondary coil 10 being connected by wire11 with one of the field-coils, the other conductor 12 leading to thebrush 8.

13 indicates a wire leading from the fieldcoil and to which the brush 18is connected by wire 14, and a shunt is formed between the conductor 13and the conductor 12 embodying the conductors 15 and 16, inductive coils17 on a closed magnetic circuit core 71, and a movable switch-arm 19,cooperating with the contacts 20 21 22 23, connected to the coils of theinductive winding and also with the contact 24, connected to the end ofsaid winding 17. The arm 19 cooperates at the extremes of movement withthe pins 31, which are so arranged that the shunt between thearmature-terminals is permanent and is never opened entirely whether themotor is operating at full speed or is at rest, although the inductivewinding is capable of variation to vary'the speed.

While it is impracticable to state exactly the proper ratio or relationexisting between the ampere-turns in the field and armature coils, asthis will vary with different motors and also with the load, we findthat the fieldmagnet windings must have a relatively high self-inductionor be designed for a relatively high electromotive force-as,forinstance,one hundred and ten volts-and the armaturewindings arelatively low self-induction or designed for a relatively lowelectromotive f0rceas, for instance, about eighteen or twenty voltsor,to express it difierently, the field might have two hundred ampere-turnsand the armature eleven and one-half ampore-turns.

While we have shown a magnet having only two pole-pieces, it is obviousthat a multipolar machine could be used.

The field-windings, armature-coils, (excepting the inductive winding,)the commutator, and brushes are connected in series, as inconstant-current motors, and when the motor is operating at full speedthe switch 19 in the shunt engages contact-point 20, so that the entireinductive winding 17 is in the shunt. By moving the switch-arm 19 fromthis position toward the contact 24 the speed of the motor may bereduced as desired, more and more of the winding-coils 17 being out ofthe shunt and a greater portion of current allowed to pass through it;but when the switch reaches the contact 24, the winding then being allcut out, the machine is short-circuited and brought to an immediatestop, and there is no tendency on the part of the armature to rotate.

In another pending application, Serial No. 710,366, we have describedand claimed the employment of a shunt across the armature of a motor ofthis type and connected in the manner described; but we find that withthe induction-winding on a closed magnetic core the regulation andcontrol of the motor are accomplished without as great a loss of energy.For instance, to operate a certain motor properly it requires thirty-sixvolts at the brushes. This would require a resistance of nine ohms atfour amperes or one hundred and forty-four Watts loss; but with ourinductive winding we accomplish the same result with 1.75 ohmsresistance at same amperes at a loss of only twenty-eight watts.

We claim as our invention- 1. In combination in a motor for alternatingcurrents, field-windings, armature-coils, commutator, andcommutator-brushes, connected in series as customary in constant-currentmotors, and an inductive winding forming a shunt around thecommutator-brushes.

2. In combination in a motor for alternating currents, field-windings,armature-coils, commutator, and commutator-brushes, connected in seriesas customary in constant-current motors, and an inductive winding woundon a closed magnetic core and forming a shunt around thecommutator-brushes.

3. In combination in a motor for alternat ing currents, field-windings,armature-coils, commutator, and commutator-brushes, connected in seriesas customary in constant-current motors, and a variable inductivewinding forming a shunt around the commutatorbrushes, adapted to varythe voltage between the armature-terminals.

4. In an electric motor for alternating currents, the combination withfield-windings designed for relatively high self-induction or relativelyhigh electromotive force, armaturecoils designed for relatively lowself-induction or relatively low electromotive force, and commutator andcommutator-brushes at the neutral point and all arranged in series, of avariable inductive winding in shunt around the armature-terminals.

OSCAR I-I. PIEPER. ALPHONSE F. PIEPER.

Witnesses:

G. WILLARD RICH, WALTER B. PAYNE.

